Sun switch



S. WILCQX SUN SWITCH May 23, 1950 Filed May 17, 1947 i/l l ms;

IN VEN TOR.

fliemczri mlcox, agvww Patented May 23, 1950 l-JNITI'ED STATES PATENTOFFICE SUN SWITCH" Stewart Wilcox, Inglewood, CaliL';

ADDlicationMay 17, 1947, Serial No. 748,793,

7 Claims. 1

This invention relates toe, sunswitch in which an-electrical switch isoperated by the presence or absence of light.

It is a primary object of this invention to provide an improved sunswitch, which is more sensitive to light and which is more accurate thanthose heretofore proposed.

There are many instances in which it is desired to automaticallycloseelectrical circuits in response to a condition of light or darkness. Oneimportant use of such a switch is to automatically control operations ofisolated beacons or other unattended lights; and the like. It hasheretofore been proposed to use bi-metallic strips, which are exposed tosunlight, to control operation of electrical switches, the heat from thesun causing the bi-metallic strip to open or close a switch. Adifiiculty that has been encountered in such switches is the necessityof providing for variations'in the ambient temperature. Obviously, suchswitches are of no value if they operate only from variationsin'temperature.

It has heretofore been suggested to use two metallic strips, one ofwhich was exposed to light and the other of which was notor one of whichwas darkened to absorbheat from light and the other of'which wasreflective, connected by suitable linkage to correct ambienttemperatures. Such linkages were sometimescomplicated and sometimes notas accurate a desired. Another defect-was that most devices, as theyoperate on the principle of thermo-dynamics, were more affectedby'brig'ht sunlight, such as at noon, and

less by reduced light,'such as sunrise and sunset.

Thuath'ere often tended to be a difference in operative efiectivenessbetween the various hours of-=the day." The critical periods ofoperation are at'sunris'e and sunset and a primary object of my'invention'isto provide a sun switch which will" be moresensit'ive at"sunrise I and sunset.

Briefly, my=switch comprises two helical bimetallic strips so connectedas'to form a continuous helix. Howevenone of the strips has the highexpansion metal'on the outside, while the otherhas the high expansionmetal on' the inside so 'that thehelices rotate in opposite directionsupon variations in temperature and this compensates-for variationsin'the ambient temperature. The helix with'th'e high expansion'metal onthe outside is paintedblack, or'some dark color, and exposed -tosunlight, while the'second helix is painted white, or some other lightcolor, to reflect sunlight and} preferably, is protected by a hoodwhlch' providesa shaded insulatedspace around-the metallic-'- element.Preferably, the

switch-i placed'in a north-south position and the hood will extendaround the second portion of the bi-metallic element, so as to protectit from sunlight.

for-it must be exposed to the sun in the early morning and late evening.

My invention will be more readily understood by reference to the drawingwhich forms a part hereof and inwhich Figure 1 represents an iso-'metric view of my invention and Figure 2 represents a vertical crosssectional View of 'my device.

Mounted on'a base plate I0 'is a transparent cylinder II which may bemade of any suitable transparent material but which, preferably, will bemade of glass. The outer end of the tube H is closed by a cap l2 whichcarries a bearing I 3 axially aligned with the tube. Itis preferred thatan insulating and sealing gasket Id be inserted between the cap and thetube in order to make it air-tight. A bearing l 5"is also provided inthe base plate and'is aligned with the first men-' tioned bearingl3,"the two bearings being adapted to receive a shaft'lfi, extendinglengthwise of the tube H and to permit it to freely slide longitudinallyas well as rotate therein. Also, mounted onthe base plate II] is a hoodll'spaced away from the transparent cylinder" ll, as shown; Preferably,this hood extends over the top of the cylinder when it'is placed in ahorizontal position, for about half its length so as to shade the topand sides of the tube, as shown. It is'also preferred that the sides ofthe hood be provided with-louvers l8, as shown; The'entire assembly,

formingwhat might be called a'casing, can-be held'togetherb'y anysuitable means, such as a plurality of tie rods l9;

Mounted on the shaft l6, in the interior of the transparent tube II, isa bi-metallic element, generally indicated by 20. The bi-metallicelement comprises two sections 2| and 22. The first section 2! is madeof a thermostatic bi-metalllc metal with the high expansion metal on theout side and is dark colored, preferably black. The

' second elementZZ is also of bi-metallic metal, but has the highexpansion metal on the inside and is light colored,preferablywhite. Thetwo sections 2 l' and 22 are rigidly secured together at the center byany'suitable means such as machine screws'23, and. at the connection areseparated by a short insulator strip'24. Obviously, the two sections ofthe bi-metallic element should be made of the same bi-metallic materialin order that their rates of expansion will be identical andb'oth'should be of the same length so that Obviously, the first portionof the "element is notshaded, at least at the sides the angle oftwisting should be identical for variations in ambient temperatures. Itwill be obvious the first section 2! will rotate in a clockwisedirection with an increase of temperature, while the second element 22will rotate counterclockwise with an increase in temperature. One end ofthe bi-metallic element 20, such as the free end of the first section2|, is rigidly attached to the cap I2, or other part of the casing, suchas by screw 25. The other end of the element 20, such as the free end ofthe second section 22, is rigidly afiixed to the shaft l6 by anysuitable means such as collar 26, to which it is aflixed, as by screw21, the collar being rigidly mounted on the shaft l6 by any suitablemeans not shown. The light colored end of the helix should be arrangedunder the hood and the dark colored portion should be unshaded, asshown.

The shaft 16 extends through the bearing l and base plate H), as shownin Figure 2. The end of the shaft I5 is flattened, as at 30 to form acam. Associated with the cam portion 30 of the shaft I6 is an electricalswitch which is moved between open and closed position by a slightmovement of a bearing member 32 which contacts the cam portion 30 onshaft l6. Many suitable switches are manufactured on the market. but onethat I have found very satisfactory is a Micro pin-type switch which isactuated by movement of the bearing member of .0003 inch. In a neutralposition the bearing member 32 will contact the flat portion of the cam30, in which case, customarily, it will be preferred that the switch beopen. It will. be obvious that as the adsorption of heat from lighttwists the bi-metallic element thereby rotating the shaft IS, thehearing member 32 of the switch 3! will be moved by rotation of theshaft to close the switch 3!.

Enclosing the switch 3! and cam is a casing which preferably is tappedand threaded as at 4| to receive an electrical conduit, not shown. Thecap 4!) can be removably attached to the base plate It! by any suitablemeans such as studs 42. In some installations it may be preferred toplace an insulating plate 43 within the cap 40 and to attach electricalbinding posts 44 and 45 thereto. These binding posts are adapted toreceive the ends of electrical power lines, not shown. The switch isconnected to the binding posts by spring members 46 and 41 which, whenthe cap and base plate are assembled engage the binding posts 44 and 45,respectively. Thus the binding posts 44 and 45 can be connected tosuitable power leads while the cap is removed from the base plate. Thenwhen the base plate H! and cap 40 are as sembled there is an automaticconnection to the switch 4! through the spring contacts 46 and 41. It isbelieved that operation of my sun switch will be obvious. In the absenceof sunlight the ambient temperature enclosing both sections of thebi-metallic element will be the same and the shaft Hi will be in aneutral position regardless of the ambient temperature. This is due tothe fact that as the two sections of the oi-metallic element are of thesame length, and have the same coeiiicient of expansion, but operate inopposite directions. ambient temperature changes thus will rotate thetwo sections equally in opposite directions, thereby neutralizing theirrotational effect. Any expansion of the metals can exert a force in alongitudinal direction without changing the setting of the switch 42.However. when the sun shines upon the first section 2| of thebi-metallic element its darkened color adsorbs heat from the light. Asthe other section '22 of the bi-metallic element is both shaded anddarkened the light will have no effect upon the second section. Thus thetotal effect of the bimetallic element will be to rotate it through aslight angle, which rotates the shaft [6 and its cam 30, thereby movingthe pin 32 of the switch 3|. With the passing of the light the firstsection will cool relative to the second and rotate the shaft and cam 30in a backward direction to again present the flattened surface 30 to thepusher rod 32.

It will be obvious to those skilled in the art that variousmodifications of my invention can be made without departing from thespirit and scope thereof. Accordingly, the appended claims are to begiven a construction commensurate with the scope thereof and as broad asis permitted by prior art.

I claim:

1. A sun switch comprising a casing having a. transparent portion, ahelical bi-metallic element of relatively small diameter in thetransparent portion, one end of which has the high expansion sideoutside and the other side of which has the 5 high expansion on theinside of the helix, one

end of said helix being painted white and the other painted black, arotatable and longitudinally displaceable shaft journaled in saidcasing, one end of said bi-metallic element being affixed to said casingand the other end of said bimetallic element being affixed to saidshaft, a cam carried by said shaft and a switch operated by said cam.

2. The apparatus of claim 1 comprising also a hood shading the whiteportion of said bi-metallic element.

3. The apparatus of claim 1 comprising also an insulator separating thetwo ends of said helix.

4. A sun switch comprising a base plate, a transparent cylinder afiixedto said base plate, a cap on said transparent cylinder, a rotatable andlongitudinally displaceable shaft axially aligned in said transparentcylinder, a two-sectioned helical bi-metallic element co-axially alignedwith said shaft, one section of which has the high expansion sideoutside and the other section of which has the high expansion on theinside of the helix, one section of said helix being painted white andthe other painted black, one end of said bi-metallic element beingafflxed to said shaft and the other end thereof being rigidly securedwith re spect to said base plate, a cam carried by said shaft and aswitch operated by said cam.

5. A sun switch comprising a transparent casing, a helical bi-metallicelement within said transparent casing, one end of which has the highexpansion side outside and the other side of which has the highexpansion on the inside of the helix, one end of said helix being lightcolored and the other dark colored, a hood superposed over the lightportion of said bi-metallic element, one end of said helix being rigidlysecured to said base casing, a longitudinally displaceable shaft keyedto the other end of said bi-metallic element, a cam carried by saidshaft and a switch operated by said cam.

6. A sun switch comprising a casing having a transparent portion, ahelical bi-metallic element within the transparent portion of saidcasing, one end of which has the high expansion side outside and theother side of which has the high expansion on the inside of the helix,one end of said helix being light colored and the other dark colored, alongitudinally displaceable cam keyed to one end of said bi-metallicelement, the other end of said helix being rigidly secured to saidcasing and a switch operated by said cam.

7. A sun switch comprising a base plate, a transparent casing afiixed tosaid base plate, a, rotatable and longitudinally displaceable shaftaxially aligned in said transparent casing, a twosectioned helicalbi-metallic element in said casing coam'ally aligned with said shaft,the two sections being of equal length and equal coefficient ofexpansion, the first section of said element being painted black andhaving the high expansion side outside and the second section of saidelement being painted white and having the high expansion side on theinside of the helix, means aflixing one end of said element to saidshaft, 15

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,461,523 Fransson July 10, 19231,641,170 Karlson Sept. 6, 1927

